The present invention relates to an interactive data transmission system including an information recording and/or reproduction apparatus connected via a bus for transmitting digital signals, and relates to a control method of this interactive data transmission system.
An interface bus, standardized according to IEEE 1394 (hereinafter referred to as a 1394 interface bus), is known as a high performance interface bus capable of realizing a data transmission rate exceeding 100 Mbps (Mbit/sec) and transmitting both video information and audio information in addition to control information.
This kind of high performance interface bus is preferably used for connecting an information recording and/or reproduction apparatus, such as VTR (video tape recorder), and an external electronic apparatus, such as a personal computer, to constitute an interactive data transmission system. Among various commands used in this interactive data transmission system, a command may be sent from the external recording apparatus to designate a tape speed during recording. Other command may relate to a judgement as to whether the signal to be recorded is a standard definition (SD) signal or a high definition (HD) signal.
However, it was impossible to designate a type of a cassette or a grade of a magnetic tape from an external electronic apparatus when a VTR has a plurality types of loadable (compatible) cassettes. For example, different kinds of cassettes, such as VHS (registered trademark) cassettes, VHS-C (registered trademark) cassettes and S-VHS (registered trademark) cassettes, are loadable in a VTR conforming to a D-VHS (registered trademark) standards. Furthermore, magnetic tapes accommodated in these different cassettes are classified into a plurality of grades, such as VHS tape, S-VHS (registered trademark) tape, D-VHS tape.
Furthermore, it was impossible for an external electronic apparatus to designate a recording by analog signals because there was a premise that the input information recordable on a magnetic tape by the information recording and/or reproduction apparatus was limited to digital data.
Furthermore, according to a VTR conforming to the D-VHS standards or the DVC standards (refer to Published Japanese Patent Application No. Kokai 7-226025), a recording region on its magnetic tape is divided into a plurality of regions including a recording region storing control information and a recording region storing main information corresponding to video and audio input information. However, it was impossible for an external electronic apparatus to designate a specific part of the divided regions on which the data are recorded (rewritten).
Furthermore, the above-described high performance interface bus can be used for connecting an information transport apparatus reproducing information recorded in a recording media, such as VTR, and an electronic apparatus, such as other VTR or a personal computer, to constitute an electronic data transmission system. Among various commands used in this electronic system, a command may be sent from other electronic apparatus to the information transport apparatus to inquire an operating condition (stopped or operated) of the information transport apparatus. Other command may be a transport state command returned from the information transport apparatus for responding to the received inquiry.
However, the 1394 interface bus does not restrict the transmission timing of the above-described transport state command for inquiring the operating condition of other electronic apparatus via the bus. This allows flexible and occasional inquiries. However, the following problems arise.
When an information transport apparatus starts transmitting a specific information (e.g., one movie program), it is important for an electronic apparatus connected to the information transport apparatus via a bus to correctly know an end time of the transmission of this specific information. To this end, it is necessary to transmit the transport state command at relatively short intervals and receive a response from the information transport apparatus. For example, it is now assumed that the information transport apparatus transmits a program of two hours (i.e., 120 minutes). When the transmission interval of the transport state command is set to 7 minutes, the number of required transmission of the transport state command is 18 times until the end of the data transmission is detected. Furthermore, there is a delay time of 6 minutes, between the actual end time of the data transmission and the detected time, due to a dormant period between the seventeenth command transmission (occurring at a 119 minutes point) and the eighteenth command transmission (occurring at a 126 minutes point). This delay time of 6 minutes will force a recording apparatus to operate unnecessarily.